// author: khba
// road to IZhO gold
#include "bits/stdc++.h"
using namespace std;
#ifdef khba
#include "debug.h"
#else
#define print(...) 42
#endif
int32_t main()
{
#ifdef khba
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
ios ::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, k; cin >> n >> k;
vector <int> a(n);
for (int &i : a) cin >> i;
k = n - k;
vector <int> d;
for (int i = 1; i < n; ++i) d.emplace_back(a[i] - a[i-1]);
sort(begin(d), end(d));
int64_t ans = n;
for (int i = 0; i < k; ++i) ans += d[i] - 1;
cout << ans;
return 0;
}
